352 MAZATLAN UNIVALVES 



401. MoDULtrS CATENTJLATUS, FJlil. 



Troclius catenulatus, Kust. Syst. Conch. Cab. p. 110, no. 122, 



pi. 18, f. L—Mke. in Zeit. f. Mai. 1850, p. 173, no. 33.— 



C. B. Ad. Pan. Shells, no. 273, p. 190. 

 Modulus catentilatus, H. Sf A. Ad. Gen. i. 317. 

 = Modulus trocLiformis, Ej/d. Sf Soul. Voy. Bonite, pi. 36, 



f. 1—5, pi. 37, f. 25-31 -.—B. M. Cat. p. 23, no. 177. 

 = Modulus Carcliedonicus, P. P. C. Cat. Prov. : — non A. Ad. 



loe. cit. : nee Monodouta carchedonius!. Lam. An. s. Vert. 



vol. ix. p. 175, no. 7, ( = T. perlatus, Dillw. = T. unidens, Chem, 



teste Desh. ; = T. unidens, D' Orb. B. M. Cat. Sagr. Col. p. 21, 



no. 233, pars.) 



The synonymy of tliis little understood genus has scarcely 

 been improved by Mr. Adams' monograph of the species in 

 the Cumingian Collection. The Lamarckian name is there 

 assigned to the M. Sajdi, Niitt. ms., said to be from "Atooi, 

 California." The genus was not found by Nuttall in California, 

 and Atooi is in the Sandwich Islands. The Lamarckian 

 species, which may be the Caribb^Ban analogue of this shell, 

 T. angulatus, C. B. Ad., or a distinct species, must revert to 

 the old Chemnitzian name, M. unidens, teste Desh. 



The Mazatlan sheU when adult has the general aspect of 

 a Trochus ; the spire bein? (mori? or less) elevated, and the 

 spire-outlines straight. The spire is covered with crowded 

 subgranulous revolving striae ; and the base, which is rarely 

 flattened, often much swoUen near the very small umbilicus, 

 has about 8 rather deeply cut grooves. .Colour varying from 

 white to light purplish brown ; generally with the latter in 

 dots. Labrum sharp, inside deeply grooved : periphery with 

 a veiy sharp keel, which in j'oung shells, or after fracture, is 

 sometimes slightly waved, scarcely tuberculous. Operculum 

 multispiral (not paucispiral, as stated in Ad. Man. loc. cit.) 

 with about 9 turns, very thin, transparent, edges irregularly 

 overlapping, rather concave outside, with the siu'face most 

 minutely granidose. The shells, though strong, had often 

 received severe fractures ; they were sometimes mcrusted, and 

 occasionally incommoded by Ostrea conchaphila. Long. '77, 

 long. spir. "48, lat. '72, div. 70". 



JIab. — Mazatlan ; not imcommon ; L'pool Sf Havre Coll. 



Tablet 1088 contains I sp. white.— 1689, 3 do. flattened.— 

 1690, 3 do. undulated.— 1691, 1 sp. ordinary state.— 1692, 3 do. 

 flattened. — 1693, 3 do. deep colour.— 1091, 3 do. undulated. — 



